/// <inheritdoc />
public FileSystem?TryLoadFileSystem(Stream stream)
{
using var reader = new BinaryReader(stream, Encoding.ASCII, true);
BiosParameterBlock?_bpb;
byte bpbOffset = 0x0B;
try
{
_bpb = BiosParameterBlock.Parse(reader, bpbOffset); //Try to parse the BPB at the standard offset
}
catch (InvalidDataException)
{
//BPB likely invalid, check if this is an Acorn 800k disk without one
if (CheckForAcorn800k(reader))
{
return(new Fat12FileSystem(stream, BiosParameterBlock.DefaultAcornParameters));
}
else
{
//BPB likely invalid, try parsing it at 0x50 in case it's an Apricot disk
try
{
bpbOffset = 0x50;
_bpb = BiosParameterBlock.Parse(reader, bpbOffset);
}
catch (InvalidDataException)
{
//BPB still invalid, it may not even be there, try to figure out if it's a DOS 1.x disk by looking at file length
//(we can do this for raw sector images) and the media descriptor byte
if (!BiosParameterBlock.DefaultParametersForSize.TryGetValue(stream.Length, out _bpb))
{
return(null);
}
}
}
}
return(GetFatFromBiosParameterBlock(stream, _bpb));
}
